1. Field
One or more embodiments relate to a fuel cell system having a fuel circulation structure, a method of operating the fuel cell system, and an electronic apparatus including the fuel cell system.
2. Description of the Related Art
A small-sized fuel cell system (hereinafter, referred to as a fuel cell system) such as a direct methanol fuel cell (DMFC) may be used as an energy supply source of household or portable electronic products.
FIG. 1 is a block diagram of a general fuel cell system. Referring to FIG. 1, the general fuel cell system includes a stack 10, a feed pump 12, a fuel concentration sensor 14, a mixer 16, a fuel flow sensor 18, a fuel pump 20, a control circuit 22, and a fuel cartridge 26, wherein the stack 10 generates power, the feed pump 12 supplies fuel having an appropriate concentration, the fuel concentration sensor 14 senses the concentration of fuel supplied to the feed pump 12 from the mixer 16, the mixer 16 dilutes high concentration fuel supplied from the fuel cartridge 26, the fuel flow sensor 18 senses the amount of the fuel supplied to the mixer 16, the fuel pump 20 supplies the fuel stored in the fuel cartridge 26 to the mixer 16, the control circuit 22 controls the operation of the fuel pump 20, and the fuel cartridge 26 stores the fuel.
In the general fuel cell system, the amount of fuel supplied to the stack 10 per hour is small. Accordingly, the fuel supplied to the mixer 16 is minutely adjusted. Accordingly, a pump (hereinafter, precision pump) that is capable of precisely supplying a very small amount of fuel is used as the fuel pump 20. However, the precision pump is expensive.
Also, in the general fuel cell system of FIG. 1, according to the movement of the general fuel cell system and/or a remaining amount of the fuel stored in the fuel cartridge 26, the pressure in the fuel cartridge 26 may be different. Accordingly, the amount of the fuel supplied to the fuel pump 20 from the fuel cartridge 26 may be different. As a result, the concentration of the fuel supplied to the stack 10 may not be uniformly controlled. Thus, the fuel flow sensor 18 and the fuel concentration sensor 14 may be inevitably included in the general fuel cell system of FIG. 1 and a fuel supply feedback process needs to be performed. Accordingly, programs for operating and controlling the fuel concentration sensor 14 and the fuel flow sensor 18 and a program for controlling the fuel supply feedback process are needed. Since the fuel pump 20, the fuel flow sensor 18, and fuel concentration sensor 14 are included in the general fuel cell system, the price of the general fuel cell system may increase.
In addition, with regard to an operation initiation, while the fuel moves from the fuel cartridge 26 to the fuel pump 20, self-priming may be delayed. When there is gas in a path between the fuel cartridge 26 and the fuel pump 20, the time taken for self-priming may be longer. In particular, when there is gas in the fuel pump 20, fuel pumping is difficult and thus self-priming may not occur.